Investigation Sequence

Title

Colored Liquids

Written by:

Robert Sweetland                 Date 2002

Focus Questions

Content
What causes liquids to flow?
What happens when the same liquids with different colors are mixed?
What happens when the same liquids with different temperatures (hot and cold) are mixed?
What happens when different liquids of different colors are mixed?

Concepts

Content: Earth, Physical, & Life

Different liquids may have different or similar densities.
Different concentrations may have different or similar densities.
Liquids of different temperatures have different densities.

Cross cutting concepts

Evidence is collected through observation.
Change is a difference in properties over time.
Very careful observations can help us notice changes we sometimes overlook.
Observations are used to collect evidence to use to explain why certain events happen.

Science Practice

Communication
Diagrams can be used to show change.
Charts help to organize information to see patterns.
Symbols may be used to communicate observations.

Experimenting
A fair experiment controls all variables and uses a control.

Personal, Social, Technology, Nature of Science, History

Other possible concepts: concentrations, temperature, expansion, volume, mass, control, variables, observation, evidence

Background information

Teacher preparation REQUIRED: The following solutions need to be made before class.

Materials:
8 small containers per group, 1-4 droppers per group, kosher salt, green, red, blue food coloring, paper towels, soapy water, hot and cold water.

Recipe for salt water solutions:
Use Kosher salt for a less cloudy solution. Add food coloring to a medium-dark solution. Light colored solutions are harder to observe.
Green 250 ml salt 1000 ml water most dense
Red 165 ml salt 1000 ml water
Clear 60 ml salt 1000 ml water
Blue None 1000 ml water least dense

To release a drop below the surface place the dropper part way into the water and squeeze. Observe if the drop rises or sinks.

Other concepts: concentration, temperature, expansion, volume, mass, control, variables, observation, evidence

A chart can be made with red, blue, clear, and green across the side and top. Label one drops and the other container. Write the results in the corresponding cell.

Activity Sequence

1. Colored drops in water.
2. Colored drops in different liquids.
3. Colored drops in different temperatures of water.
4. Colored drops in colored liquids.

Activity Descriptions

1. Colored drops in water:
Materials:
Red and blue food coloring, dropper, 4 small containers, water, and soapy water

  1. Ask what will happen when a drop of red or blue food coloring is released in plain water. (RELEASED could be above or below the surface.)
  2. Write predictions on the board.
  3. Ask students how they could chart their observations.
  4. Have students do the following and record their observations.
  5. Put plain water in a small container.
  6. Squeeze a drop of red food coloring into the water.
  7. Record observations and explain what happened.
  8. Rinse the dropper.
  9. Put the same amount of water in the second container.
  10. Add a drop of blue food coloring to the water.
  11. Record your observation and explain what happened.
  12. Have the class discuss what happened.
  13. Ask students to discuss what changed when red and blue food coloring were added to the water.
  14. Ask what variables were the same or controlled and what variable changed?
  15. Discuss why the results were the same or different.
  16. Ask how the chart helped them understand or use their observations.

2. Colored drops in different liquids:
Materials:
Food coloring, 2 droppers, 4 small containers, salt water, soapy water

  1. Ask what will happen when a drop of blue or red food coloring is released in salt water? (RELEASED could be above or below the surface.)
  2. Write prediction on the board.
  3. Ask students how they could chart their observations.
  4. Have students do the following and record their observations.
  5. Put salt water in a small container.
  6. Squeeze a drop of red food coloring into the salt water.
  7. Record observations and explain what happened.
  8. Rinse the dropper.
  9. Put the same amount of salt water in the second container.
  10. Add a drop of blue food coloring to the salt water.
  11. Record your observation and explain what happened.
  12. Have the class discuss what happened.
  13. Ask students to discuss what changed when red and blue food coloring were added to the salt water.
  14. Ask what variables were the same or controlled and what variable changed?
  15. Discuss why the results were the same or different.
  16. Ask if the chart helped.
  17. Ask how the observations of food coloring in salt water compare to the observations of food coloring in plain water?

3. Colored drops in different temperatures of water:
Materials:
Food coloring, 2 droppers, 4 small containers, hot and cold water, soapy water

  1. Ask what will happen when a drop of blue or red food coloring is added to hot or cold water? (RELEASED could be above or below the surface.)
  2. Write prediction on the board.
  3. Ask students how they could chart their observations.
  4. Have students do the following and record their observations.
  5. Put the same amount of hot water and cold water in two small containers.
  6. Squeeze a drop of red food coloring into each.
  7. Record observations and explain what happened.
  8. Rinse the dropper.
  9. Put the same amount of hot water and cold water in two other containers.
  10. Add a drop of blue food coloring to each.
  11. Record observations and explain what happened.
  12. If you released all the drops above water, then repeat all of the above by releasing the drops below the surface of the hot and cold water..
  13. Record the observation and explain what happened.
  14. Have the class discuss all the results.
  15. Ask students to discuss what changed when the temperature of the water changed.
  16. Ask what happened when drops were released below the surface?
  17. Ask what variables were the same or controlled and what variable changed?
  18. Discuss why the results were the same or different.
  19. Ask how they had to change their chart.
  20. Ask how these observations compared with the previous activities.

4. Colored drops in different colored liquids:

Materials:
Green, red, blue, and clear solutions, droppers, 4-8 small containers, water, soapy water

  1. Challenge the students to think of how they could combine the four different liquids.
  2. Write their suggestions on the board.
  3. Ask how they could make a chart to show what happened when each liquid was released in each other liquid both above the surface and below the surface.
  4. Suggestion: If the drop goes down in a liquid, use an arrow pointing down. If a drop goes up, use an arrow pointing up . If a drop spreads, use a circle
  5. Test all possible combinations of colors.
  6. Put results on the chart.
  7. What can you conclude about the four liquids?
  8. If you had equal volumes of the four liquids, which would be the heaviest (most dense)?
  9. Rank the liquids in order from heaviest to lightest (greatest to least density).
  10. What did you learn about evidence and how important it is to collect good evidence to make explanations?
  11. What did you learn about making charts to record observations and understand data.

Dr. Robert Sweetland's notes